Frequency division multiple access (FDMA) or orthogonal frequency-division multiplexing (OFDM) waveforms may utilize redundancy schemes such as cyclic prefixes (CPs) or null subcarriers to account for variable channel delay spreads in order to provide reliable communications. However, resources and energy may be wasted since a CP size is sometimes fixed and determined by a worst channel delay spread of a cell at a particular time. A CP also wastes energy since CP duration is unused and the CP is discarded at a receiver. The CP size may also need to be communicated to a wireless transmit/receive unit (WTRU) before transmissions begin in a cell creating overhead and connection delays. Thus, CPs consume extra energy, waste resources, and create overhead.
Furthermore, to achieve reliable communications, low peak-to-average power ratio (PAPR) characteristics, lower out-of-band (OOB) leakage, very high data rates, and better quality of experience (QoE), next generation of wireless and wired networks utilizing FDMA or OFDM will require improved management of different delay spreads and other channel conditions. Thus, it is desirable to have FDMA or OFDM communications that account for delay spreads with better resource management and reduced signaling overhead.